The invention relates to an implantable hearing aid for stimulation of the inner ear.
In a known hearing aid for stimulation of the inner ear (German Offenlegungsschrift 28 25 233), the subassemblies forming the hearing aid, including a tritium battery, are hermetically encapsulated and are placed in the external auditory canal or are implanted in the mastoid, and the hearing aid is connected by an electric line directly to the auditory nerve on the output side. In a modified embodiment of the known aid, acoustic vibrations generated by the hearing aid implanted in the mastoid are transmitted by the mastoid-bone process into the middle ear by exploiting the fact that this bone exhibits hollow spaces that are connected to the middle ear by the vestibular window.
In another known hearing aid (European Application 242 038 A2), a microphone, an amplifier, a battery, a volume control and an excitation coil, for a magnet that is fastened to one of the auditory ossicles, are placed in a housing that is to be inserted into the external auditory canal. Further, a hearing aid is known (British Patent 1 440 724) in which a microphone, an amplifier and a battery are arranged in a housing that is inserted in a plug-like manner into a base and is implanted in the temporal bone behind the external ear. The output signal of the amplifier goes to an excitation coil, implanted in the middle ear, of a magnet fastened to the stirrup bone.
Further, a hearing aid is known (U.S. Pat. No. 4,532,930) in which, by an implantable electrode arrangement, a direct electrical stimulation of the inner ear occurs with the aid of signals that are made available by a suitable signal processing electronic device. Here the signal processing electronic device is placed in a relatively large-volume housing that is carried along externally in a separate pocket. The signal processing electronic device is connected by a connecting cable to a transmitting antenna that is placed in the area of the ear in question.
In the known hearing aids, the achievable sound quality often leaves something to be desired. Adaptation problems can occur, and the stimulation by a magnet fastened to an auditory ossicle makes necessary an intervention in the chain of auditory ossicles that poses risks.